Seasonal Changes of Fat Content of Milk of Black-and-White Cows
K. KRASTEV, V. GAYDARSKA and I. YANCHEV
Institute of Animal Breeding, BG-2052 Kostinbrod, Bulgaria
KRASTEV, K., V. GAYDARSKA and I. YANCHEV, 2000. Seasonal changes of fat content of milk of Black-and-white cows. Bulg. J. Agric. Sci., 6: 697-700
The effect of abiotic ecological factors (temperature, relative humidity and air velocity in the barn) by season on fat content of milk of clinically healthy Black-and-white cows for a normal 305-day lactation was studied.
The animals were raised year-round tied in a barn, constructed of concrete steel panels with natural ventilation. Excrements were disposed of by flat-chain transporter. Cows were milked by aggregates in milk-cans, watered in individual watering-troughs and fed in cement cribs.
It was established that the biological regularity of milk fat content increase at the end of the lactation period is directly influenced by the season of the year, which is a sum ecological factor. When lactation is coming to an end in autumn and winter, this regularity is enhanced by the effect of low temperature and increased humidity. On the contrary, cows with the second half of lactation in spring and summer show that the biological regularity is inhibited and fat content is either maintained or decreasing under the influence of higher temperature and low humidity of the production environment.
Key words: milk fat content, Black-and-white cows, seasonal changes